Device and method for controlling internal combustion engine

ABSTRACT

When an ignition switch is turned off, an ECU executes a program including the steps of: stopping an engine; setting a phase of an intake camshaft (or a phase in which an intake valve opens/closes) to be a maximally retarded phase; advancing the phase of the intake camshaft; detecting the phase of the intake camshaft as based on a number or rotations of an electric motor of an intake VVT mechanism changing the phase of the intake camshaft; and, if the phase detected as based on the number or rotations of the electric motor is advanced to a target phase, stopping changing the phase of the intake camshaft.

This nonprovisional application is based on Japanese Patent Application No. 2006-019599 filed with the Japan Patent Office on Jan. 27, 2006, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to devices and methods for controlling internal combustion engines and particularly to techniques employed to control internal combustion engines in which a phase in which at least one of intake and exhaust valves is opened/closed is varied.

2. Description of the Background Art

Conventionally there have been known Variable Valve Timing (VVT) changing in accordance with a condition of operation a phase in which intake and exhaust valves open/close (or a crank angle), variable valve lift (VVL) changing an amount in which a valve is lifted, and other variable valve mechanisms changing how a valve is operated. Such variable valve mechanisms allow a valve to operate in a state (or have a phase or be lifted in an amount) appropriately corresponding to a condition of operation of interest to provide increased output, improved emission performance, and the like. While an engine is in operation, a valve is operated in a state, which is not necessarily appropriate for starting the engine. For example, if, with the engine in operation, timing the valve to close is controlled to be maximally retarded, and in that condition the engine is stopped, then, in subsequently starting the engine, an insufficiently compressed air fuel mixture can be provided. This can results in impaired startability. Accordingly a technique has been proposed to change, while stopping an engine, how a valve is operated.

Japanese Patent Laying-Open No. 2003-184585 discloses a control device for an internal combustion engine, that controls, while stopping the engine, a condition of an operation opening/closing a valve (or how the valve is operated) to be that condition of such operation which is targeted for automatically stopping an engine (an internal combustion engine). As disclosed in the publication, the control device includes: a variable valve control unit varying a condition of an operation opening/closing an intake valve or both intake and exhaust valves of the internal combustion engine to at least control intake air in amount; a control unit automatically stopping the engine when a predetermined condition for automatically stopping the engine is established while the internal combustion engine is in operation; a control unit controlling a valve in automatically stopping the engine, that calculates that condition of the operation opening/closing the valve which is targeted for automatically stopping the engine, as based on the current condition of the internal combustion engine and/or the vehicle, immediately after the control unit automatically stopping the engine automatically stops the internal combustion engine, and that controls a condition of the operation opening/closing the valve to be that of such operation which is targeted for automatically stopping the engine. As the condition of the operation opening/closing the valve that is targeted for automatically stopping the engine, the control unit controlling a valve in automatically stopping the engine calculates a condition of such operation which is estimated to be optimal for subsequently, automatically starting the engine.

As disclosed in the publication, immediately after the internal combustion engine is automatically stopped, the control device calculates from the current condition of the internal combustion engine, that of the vehicle and the like a condition of an operation opening/closing the valve which is estimated to be optimal for subsequently, automatically starting the engine as that of such operation which is targeted for automatically stopping the engine. While the engine is stopped, a condition of the operation opening/closing the valve is controlled to match that of such operation which is targeted. This allows the engine to subsequently, automatically start with the valve opened/closed in a condition which is substantially optimal for automatically starting the engine to improve the engine in automatic startability and also reduce emissions provided in automatically starting the engine.

Generally the phase of an intake or exhaust valve or the like is detected as based on a pulse signal provided from a cam position sensor employing an electromagnetic pickup sensor. The cam position sensor outputs the pulse signal as an air gap varies that is formed between the cam position sensor and a cam angle sensor plate rotating together with a camshaft. However, when the engine stops, the cam angle sensor plate (or the camshaft) rotates slowly or has a rotational speed of zero, and the air gap hardly varies and the pulse signal is hardly obtained. If the control device for an internal combustion engine as disclosed in Japanese Patent Laying-Open No. 2003-184585 is applied to change, while stopping the internal combustion engine, a phase in which a valve opens/closes, the phase is hardly detected. As a consequence, the phase in which the valve is opened/closed cannot be controlled with precision.

SUMMARY OF THE INVENTION

The present invention contemplates a control device or the like for an internal combustion engine, that can control with precision, while stopping an internal combustion engine, a phase in which intake and exhaust valves open/close.

The present invention in one aspect provides a control device for an internal combustion engine provided with a mechanism changing a phase in which at least one valve of an intake valve and an exhaust valve opens/closes. The control device includes an operation unit. The operation unit: controls the mechanism to change the phase when a predetermined condition associated with stopping the internal combustion engine is satisfied; detects an amount by which the mechanism is operated when the mechanism is controlled to change the phase; detects the phase based on the amount; and controls the mechanism to change the phase detected as based on the amount to attain a predetermined value.

In accordance with the present invention when a predetermined condition associated with stopping an internal combustion engine is satisfied a phase in which intake and exhaust valves open/close is changed. For example the phase is changed to attain a value appropriate for subsequently starting the internal combustion engine. However, with the internal combustion engine stopped, or immediately before the engine stops, the crankshaft (or the camshaft) has an extremely low rotational speed. In this condition, the phase is hardly detected with a cam position sensor employing an electromagnetic pickup sensor or the like. Accordingly, the amount by which a mechanism changing the phase is operated is detected and from the amount detected, the phase is detected. For example, a relationship between the amount by which the mechanism is operated and the phase's variation is previously obtained through an experiment or the like and stored in the form of a map which is used to detect the phase's variation. From the variation as detected and the current phase (e.g., a phase detected when it is detectable by a cam position senor, a phase that can be obtained mechanically, or the like), the changed phase is detected. A phase in which the intake and exhaust valves open/close can thus be obtained with precision without the cam position sensor. The phase thus detected is changed until it attains a predetermined value. The phase in which the intake and exhaust valves open/close can thus be changed to the predetermined value with precision. A control device for an internal combustion engine can thus be provided that allows a phase in which the intake and exhaust valves open/close to be controlled with precision while the internal combustion engine is stopped.

Preferably the operation unit controls the mechanism to change the phase after the internal combustion engine is stopped if the predetermined condition is satisfied.

In accordance with the present invention a phase in which a valve opens/closes is changed after the internal combustion engine is stopped. This can prevent the valve from opening/closing in a phase that would not be appropriate for the internal combustion engine in operation while the internal combustion engine is in operation. The phase in which the intake and exhaust valves open/close can thus be controlled in accordance with a condition of operation of interest with precision.

Still preferably, the mechanism includes a motor electrically operated and having an output shaft rotating to change the phase in which the valve opens/closes, and the operation unit detects a number of rotations of the output shaft of the motor accumulated and detects the phase as based on the number of rotations of the output shaft of the motor accumulated.

In accordance with the present invention the phase in which a valve opens/closes is changed as an electric motor's output shaft rotates. The phase is detected as based on the number of rotations of the output shaft of the motor accumulated. The phase in which the intake and exhaust valves open/close can thus be obtained with precision without the cam position sensor and hence controlled with precision.

The present invention in another aspect provides a control device for an internal combustion engine provided with a mechanism changing a phase in which at least one valve of an intake valve and an exhaust valve opens/closes. The control device includes an operation unit. The operation unit: controls the mechanism to change the phase to attain a limit value when a predetermined condition associated with stopping the internal combustion engine is satisfied, the limit value being one of values of maximally retarded and advanced angles, respectively; controls the mechanism to change the phase from the limit value if the predetermined condition is satisfied; detects an amount by which the mechanism is operated when the mechanism is controlled to change the phase from the limit value; detects the phase based on the amount; and controls the mechanism to change the phase detected as based on the amount to attain a predetermined value.

In accordance with the present invention when a predetermined condition associated with stopping an internal combustion engine is satisfied a phase is changed to a limit value. The limit value is one of values of maximally retarded and advanced angles, respectively, and mechanically determined by the structure of the mechanism and can be obtained previously. The phase in which a valve opens/closes that is set at the limit value can eliminate the necessity of employing a sensor or the like to detect the phase with precision. Such limit value is used as a reference to change the phase. For example the phase is changed to attain a value appropriate for subsequently starting the internal combustion engine. However, with the internal combustion engine stopped, or immediately before the engine stops, the crankshaft (or the camshaft) has an extremely low rotational speed. In this condition, the phase is hardly detected with a cam position sensor employing an electromagnetic pickup sensor or the like. Accordingly, the amount by which a mechanism changing the phase is operated is detected and from the amount detected, the phase is detected. For example, a relationship between the amount by which the mechanism is operated and the phase is previously obtained through an experiment or the like and stored in the form of a map which is used to detect the phase's variation. From the variation as detected and the limit value, the changed phase is detected. A phase in which the intake and exhaust valves open/close can thus be obtained with precision without the cam position sensor. The phase thus detected is changed until it attains a predetermined value. The phase in which the intake and exhaust valves open/close can thus be changed to the predetermined value with precision. A control device for an internal combustion engine can thus be provided that allows a phase in which the intake and exhaust valves open/close to be controlled with precision while the internal combustion engine is stopped.

Preferably, the operation unit controls the mechanism to change the phase to the limit value after the internal combustion engine is stopped if the predetermined condition is satisfied, and the operation unit controls the mechanism to change the phase from the limit value after the internal combustion engine is stopped if the predetermined condition is satisfied.

In accordance with the present invention after the internal combustion engine is stopped the phase is changed to the limit value, and subsequently from that limit value the phase is changed. This can prevent the valve from opening/closing in a phase that would not be appropriate for the internal combustion engine in operation while the internal combustion engine is in operation. The phase in which the intake and exhaust valves open/close can thus be controlled in accordance with a condition of operation of interest with precision.

Still preferably, the mechanism includes a motor electrically operated and having an output shaft rotating to change the phase in which the valve opens/closes, and the operation unit detects a number of rotations of the output shaft of the motor accumulated and detects the phase as based on the number of rotations of the output shaft of the motor accumulated.

In accordance with the present invention the phase in which a valve opens/closes is changed as an electric motor's output shaft rotates. The phase is detected as based on the number of rotations of the output shaft of the motor accumulated. The phase in which the intake and exhaust valves open/close can thus be obtained with precision without the cam position sensor and hence controlled with precision.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a configuration of an engine of a vehicle with an ECU a control device of an embodiment, mounted therein.

FIG. 2 shows a map defining a target value of a phase of an intake camshaft.

FIG. 3 is a flowchart representing a structure of a program for control executed by the ECU shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, an embodiment of the present invention will be described hereinafter. In the following description, like components are denoted by like reference characters. They are also named identically and function identically. Therefore, a detailed description thereof will not be repeated.

Referring to FIG. 1, a description is given of an engine of a vehicle having a control device mounted therein according to the embodiment of the present invention. In the present embodiment the control device is implemented by a program executed for example by an electronic control unit (ECU) 4000 shown in FIG. 1.

An engine 1000 is a V-type, 8-cylinder engine having an “A” bank 1010 and a “B” bank 1012 each including a group of four cylinders. Here, any engine other than the V8 engine may be employed.

Into engine 1000, air is sucked from an air cleaner 1020. The quantity of air sucked is adjusted by a throttle valve 1030. Throttle valve 1030 is an electronic throttle valve driven by a motor.

The air is mixed with fuel in a cylinder 1040 (or combustion chamber). Into cylinder 1040, the fuel is directly injected from an injector 1050. In other words, injection holes of injector 1050 are provided within cylinder 1040.

The fuel is injected in the intake stroke. When the fuel is injected is not limited to the intake stroke. Further, in the present embodiment, engine 1000 is described as a direct-injection engine having injection holes of injector 1050 that are disposed within cylinder 1040. However, in addition to direct-injection (in-cylinder) injector 1050, a port injector may be provided. Moreover, only the port injector may be provided.

The air-fuel mixture in cylinder 1040 is ignited by a spark plug 1060 and accordingly burned. The air-fuel mixture after burned, namely exhaust gas, is cleaned by a three-way catalyst 1070 and thereafter discharged to the outside of the vehicle. The air-fuel mixture is burned to press down a piston 1080 and thereby rotate a crankshaft 1090.

At the top of cylinder 1040, an intake valve 1100 and an exhaust valve 1110 are provided. Intake valve 1100 is driven by an intake camshaft 1120. Exhaust valve 1110 is driven by an exhaust camshaft 1130. Intake camshaft 1120 and exhaust camshaft 1130 are coupled by a chain, a gear and/or the like to be rotated at the same rotational speed.

Intake valve 1100 has its phase (or is timed to open/close, as) controlled by an intake VVT mechanism 2000 provided to intake camshaft 1120. Exhaust valve 1110 has its phase (or is timed to open/close, as) controlled by an exhaust VVT mechanism 3000 provided to exhaust camshaft 1130.

In the present embodiment, intake camshaft 1120 and exhaust camshaft 1130 are rotated by the VVT mechanisms to time intake valve 1100 and exhaust valve 1110, as controlled, to open/close. Note that the valves may be timed, as controlled in a method different than above, to open/close.

Intake VVT mechanism 2000 is operated by an electric motor 2010 having an output shaft connected to intake camshaft 1120 via a speed reducer (not shown) of intake VVT mechanism 2000. The speed reducer is configured of a link, a gear and/or the like.

Electric motor 2060 is controlled by ECU 4000. The current and voltage of electric motor 2060 are detected by an ammeter (not shown) and a voltmeter (not shown) and the measurements are input to ECU 4000.

Exhaust VVT mechanism 3000 is hydraulically operated. Note that intake VVT mechanism 2000 may be hydraulically operated. Furthermore, exhaust VVT mechanism 3000 may be operated by an electric motor. Furthermore the hydraulic pressure generated by an electric motor may be employed to operate intake and exhaust VVT mechanisms 2000 and 3000. The VVT mechanism can be implemented by known technology and accordingly, will not be described repeatedly in detail.

ECU 4000 receives a signal from a crank angle sensor 5000 indicating the rotational speed and crank angle of crankshaft 1090. Further, ECU 4000 receives a signal from a cam position sensor 5010 indicating a phase of intake and exhaust camshafts 1120 and 1130 (or the position of the camshaft in the direction of rotation).

Crank angle sensor 5000 and cam position sensor 5010 are electromagnetic pickup sensors and output a pulse signal to ECU 4000.

Crank angle sensor 5000 outputs the pulse signal as an air gap formed between the sensor and a timing rotor rotating together with crank shaft 1090 varies. Cam position sensor 5010 outputs the pulse signal as an air gap formed between the sensor and a cam angle sensor plate rotating together with the camshaft varies.

Furthermore ECU 4000 receives a pulse signal from a rotational speed sensor 5012 indicating the rotational speed of the output shaft of electric motor 2010 of intake VVT mechanism 2000, a signal from a coolant temperature sensor 5020 indicating the water (or coolant) temperature of engine 1000, and a signal from an airflow meter 5030 indicating the quantity of intake air of engine 1000 (i.e., the quantity of air taken or sucked into engine 1000). Furthermore ECU 4000 receives a signal from an ignition switch 5040 indicating that ignition switch 5040 is turned on or off.

Based on these signals received from the sensors as well as a map and a program stored in a memory (not shown), ECU 4000 controls: the throttle angle; the timing of ignition; the timing of injection of fuel; the quantity of fuel injected; timing intake and exhaust valves 1100 and 1110 to open/close; and the like so that engine 1000 is operated in a desired operating state.

In the present embodiment, ECU 4000 determines the phase of intake camshaft 1120 (or how intake valve 1100 should be timed to open/close) based on a map employing engine speed NE and intake air quantity KL as parameters, as shown in FIG. 2. A plurality of maps for respective coolant temperatures are stored for determining the phase of intake camshaft 1120.

Reference will now be made to FIG. 3 to describe a structure of a program for control executed by ECU 4000 in the present embodiment.

In step (S) 100 ECU 4000 determines whether ignition switch 5040 is turned off. If so (YES in S100) the control proceeds with S200. Otherwise (NO in S100) the process ends.

In S200 ECU 4000 stops engine 1000. In S300 ECU 4000 sets the phase of intake camshaft 1120 (a phase in which intake valve 1100 opens/closes) to be a maximally retarded phase for example by retarding the phase until the voltage of electric motor 2010 rapidly increases (or a lock voltage is detected).

In S400 ECU 4000 advances the phase of intake camshaft 1120. In S500 ECU 4000 detects the phase of intake camshaft 1120 based on the rotational speed of electric motor 2010 as detected by rotational speed sensor 5012.

More specifically, a map storing a relationship between a number of rotations of motor 2010 accumulated from a state with intake camshaft 1120 having the maximally retarded phase and the phase's variation is used to detect the variation of the phase of intake camshaft 1120. From the variation of the phase as detected and the maximally retarded phase (for example by adding together the maximally retarded phase and the variation of the phase as detected, or subtracting the variation of the phase as detected from the maximally retarded phase) a phase obtained after the advance (or change) is detected. Note that the phase of intake camshaft 1120 may be detected in a method other than described above.

In S600 ECU 4000 determines the phase of intake camshaft 1120 as detected from the rotational speed of electric motor 2010 has advanced to a predetermined target phase. If the detected phase and the target phase have a difference having a predetermined value or smaller, ECU 4000 determines that the phase of intake camshaft 1120 detected has advanced to the predetermined target phase. Note that the target phase is a phase determined as a phase appropriate for subsequently starting the engine. The phase appropriate for starting the engine is set with startability and emission performance considered.

If the detected phase has advanced to the target phase (YES in S600) the control proceeds with S700. Otherwise (NO in S600) the control returns to S400.

In S700 ECU 4000 stops changing the phase of intake camshaft 1120. More specifically, electric motor 2010 is stopped from operating and the phase of intake camshaft is maintained. Subsequently the process ends.

As based on the structure and flowchart as described above, the control device in the present embodiment, or ECU 4000, operates as will be described hereinafter.

To stop engine 1000 the driver turns off ignition switch 5040 (YES in S100). In response, engine 1000 is stopped (S200). If at that time intake camshaft 1120 has a phase for example maximally retarded and thus held, then, in subsequently starting the engine, an insufficiently compressed air fuel mixture can be provided. This impairs startability.

Accordingly, desirably, as engine 1000 is stopped, the phase of intake camshaft 1120 is changed to attain a target phase determined as a phase appropriate for subsequently starting the engine.

When engine 1000 stops, however, intake camshaft 1120 does not rotate. Cam position sensor 5010 employing an electromagnetic pickup sensor cannot detect the phase of intake camshaft 1120, and the phase of intake camshaft 1120 may not be changed to the target phase with precision.

Accordingly when engine 1000 is stopped the phase of intake camshaft 1120 is once set to be the maximally retarded phase (S300). The maximally retarded phase is a phase mechanically determined by the structure of intake VVT mechanism 2000. Previously storing the maximally retarded phase for example in memory allows the maximally retarded phase to be detected without cam position sensor 5010.

With this phase as a reference, the phase of intake camshaft 1120 is advanced (S400). The phase of intake camshaft 1120 advanced is detected as based on the number of rotations of electric motor 2010 accumulated, as detected by rotational speed sensor 5012 (S500). More specifically, A variation from the maximally retarded phase is detected to detect the phase of intake camshaft 1120.

Thus the phase of intake camshaft 1120 can be detected without cam position sensor 5010. In particular, in the present embodiment, electric motor 2010 has its output shaft connected to intake camshaft 1120 via a speed reducer. Accordingly, electric motor 2010 has a sufficiently high rotational speed (or a large number of rotations accumulated) in changing the phase of intake camshaft 1120. As such, the rotational speed (or the number of rotations) of electric motor 2010 (accumulated) is sufficiently (or with high precision) detectable by rotational speed sensor 5012. The phase of intake camshaft 1120 can thus be detected with precision from the number of rotations of electric motor 2010 accumulated.

If the phase thus detected has advanced to the target phase (YES in S600) changing the phase is stopped (S700). The phase of intake camshaft 1120 can thus be set to be a phase appropriate for subsequently starting the engine.

Thus the present embodiment provides a control device or ECU operating so that when the ignition switch is turned off to stop the engine the phase of the intake camshaft is once set to be a maximally retarded phase. While the phase of the intake camshaft is advanced with the maximally retarded phase serving as a reference, the phase of the intake camshaft is detected as based on the number of rotations of an electric motor of an intake VVT mechanism accumulated. This allows the phase of the intake camshaft to be detected if a pulse signal is not obtained from a cam position sensor. The phase of the intake camshaft can thus be controlled with precision.

Note that while in the present embodiment engine 1000 is stopped in response to ignition switch 5040 being turned off, engine 1000 may be stopped when the vehicle has a vehicular speed of “0” and the brake pedal is also depressed, i.e., an idle-stop condition, or an other stop condition is satisfied.

Furthermore, changing the phase of intake camshaft 1120 after engine 1000 is stopped may be replaced with changing the phase of intake camshaft 1120 if ignition switch 5040 is turned off or the idle-stop condition or a similar stop condition is satisfied or the like and before engine 1000 is stopped.

Furthermore, the phase of intake camshaft 1120 may be changed immediately before engine 1000 is started.

Furthermore, setting the phase of intake camshaft 1120 to be a maximally retarded phase may be replaced with setting the phase of intake camshaft 1120 to be a maximally advanced phase and subsequently retarding the phase to a target phase.

Furthermore, a target phase and the current phase of intake camshaft 1120 may be compared and from a result thereof whether the phase of intake camshaft 1120 should be set to be a maximally retarded phase or a maximally advanced phase may be determined. Such decision may be made to reduce the total variation of the phase.

Furthermore, the phase of intake camshaft 1120 may be changed to a target phase, rather than set to be a maximally retarded or advanced phase. The phase of the intake camshaft 1120 having been changed may be detected from that detected by cam position sensor 5010 before the phase is changed, and the variation of the phase as detected as based on the cumulative rotational speed of electric motor 2010.

Furthermore, a parameter other than the rotational speed (or the number of rotations) of electric motor 2010 (accumulated) may be employed to detect the variation of the phase.

Furthermore when engine 1000 is stopped the phase of exhaust camshaft 1130 (or a phase in which exhaust valve 1110 opens/closes) may be changed. The phase of exhaust camshaft 1130 may be detected similarly as that of intake camshaft 1120 is detected.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims. 

1. A control device for an internal combustion engine provided with a mechanism changing a phase in which at least one valve of an intake valve and an exhaust valve opens/closes, comprising an operation unit, wherein: said operation unit controls said mechanism to change said phase when a predetermined condition associated with stopping said internal combustion engine is satisfied; said operation unit detects an amount by which said mechanism is operated when said mechanism is controlled to change said phase; said operation unit detects said phase based on said amount; and said operation unit controls said mechanism to change said phase detected as based on said amount to attain a predetermined value.
 2. The control device for an internal combustion engine according to claim 1, wherein said operation unit controls said mechanism to change said phase after said internal combustion engine is stopped if said predetermined condition is satisfied.
 3. The control device for an internal combustion engine according to claim 1, wherein: said mechanism includes a motor electrically operated and having an output shaft rotating to change said phase in which said valve opens/closes; and said operation unit detects a number of rotations of said output shaft of said motor accumulated and detects said phase as based on said number of rotations of said output shaft of said motor accumulated.
 4. A control device for an internal combustion engine provided with a mechanism changing a phase in which at least one valve of an intake valve and an exhaust valve opens/closes, comprising an operation unit, wherein: said operation unit controls said mechanism to change said phase to attain a limit value when a predetermined condition associated with stopping said internal combustion engine is satisfied, said limit value being one of values of maximally retarded and advanced angles, respectively; said operation unit controls said mechanism to change said phase from said limit value if said predetermined condition is satisfied; said operation unit detects an amount by which said mechanism is operated when said mechanism is controlled to change said phase from said limit value; said operation unit detects said phase based on said amount; and said operation unit controls said mechanism to change said phase detected as based on said amount to attain a predetermined value.
 5. The control device for an internal combustion engine according to claim 4, wherein: said operation unit controls said mechanism to change said phase to said limit value after said internal combustion engine is stopped if said predetermined condition is satisfied; and said operation unit controls said mechanism to change said phase from said limit value after said internal combustion engine is stopped if said predetermined condition is satisfied.
 6. The control device for an internal combustion engine according to claim 4, wherein: said mechanism includes a motor electrically operated and having an output shaft rotating to change said phase in which said valve opens/closes; and said operation unit detects a number of rotations of said output shaft of said motor accumulated and detects said phase as based on said number of rotations of said output shaft of said motor accumulated.
 7. A method of controlling an internal combustion engine provided with a mechanism changing a phase in which at least one valve of an intake valve and an exhaust valve opens/closes, comprising the steps of: controlling said mechanism to change said phase when a predetermined condition associated with stopping said internal combustion engine is satisfied; detecting an amount by which said mechanism is operated when said mechanism is controlled to change said phase; and detecting said phase based on said amount, wherein the step of controlling said mechanism includes the step of controlling said mechanism to change said phase detected in the step of detecting said phase to attain a predetermined value.
 8. The method of controlling an internal combustion engine according to claim 7, wherein the step of controlling said mechanism includes the step of controlling said mechanism to change said phase after said internal combustion engine is stopped if said predetermined condition is satisfied.
 9. The method of controlling an internal combustion engine according to claim 7, wherein: said mechanism includes a motor electrically operated and having an output shaft rotating to change said phase in which said valve opens/closes; the step of detecting said amount includes the step of detecting a number of rotations of said output shaft of said motor accumulated; and the step of detecting said phase includes the step of detecting said phase as based on said number of rotations of said output shaft of said motor accumulated.
 10. A method of controlling an internal combustion engine provided with a mechanism changing a phase in which at least one valve of an intake valve and an exhaust valve opens/closes, comprising the steps of: controlling said mechanism to change said phase to a limit value when a predetermined condition associated with stopping said internal combustion engine is satisfied, said limit value being one of values of maximally retarded and advanced angles, respectively; controlling said mechanism to change said phase from said limit value when said predetermined condition is satisfied, detecting an amount by which said mechanism is operated when said mechanism is controlled to change said phase from said limit value; and detecting said phase based on said amount, wherein the step of controlling said mechanism to change said phase from said limit value includes the step of controlling said mechanism to change said phase detected as based on said amount to attain a predetermined value.
 11. The method of controlling an internal combustion engine according to claim 10, wherein: the step of controlling said mechanism to change said phase to said limit value includes the step of controlling said mechanism to change said phase to said limit value after said internal combustion engine is stopped if said predetermined condition is satisfied; and the step of controlling said mechanism to change said phase from said limit value includes the step of controlling said mechanism to change said phase from said limit value after said internal combustion engine is stopped if said predetermined condition is satisfied.
 12. The method of controlling an internal combustion engine according to claim 10, wherein: said mechanism includes a motor electrically operated and having an output shaft rotating to change said phase in which said valve opens/closes; the step of detecting said amount includes the step of detecting a number of rotations of said output shaft of said motor accumulated; and the step of detecting said phase includes the step of detecting said phase as based on said number of rotations of said output shaft of said motor accumulated.
 13. A control device for an internal combustion engine provided with a mechanism changing a phase in which at least one valve of an intake valve and an exhaust valve opens/closes, comprising: control means for controlling said mechanism to change said phase when a predetermined condition associated with stopping said internal combustion engine is satisfied; first detection means for detecting an amount by which said mechanism is operated when said mechanism is controlled by said control means; and second detection means for detecting said phase based on said amount, wherein said control means includes means for controlling said mechanism to change said phase detected by said second detection means to attain a predetermined value.
 14. The control device for an internal combustion engine according to claim 13, wherein said control means includes means for controlling said mechanism to change said phase after said internal combustion engine is stopped if said predetermined condition is satisfied.
 15. The control device for an internal combustion engine according to claim 13, wherein: said mechanism includes a motor electrically operated and having an output shaft rotating to change said phase in which said valve opens/closes; said first detection means includes means for detecting a number of rotations of said output shaft of said motor accumulated; and said second detection means includes means for detecting said phase as based on said number of rotations of said output shaft of said motor accumulated.
 16. A control device for an internal combustion engine provided with a mechanism changing a phase in which at least one valve of an intake valve and an exhaust valve opens/closes, comprising: first control means for controlling said mechanism to change said phase to attain a limit value when a predetermined condition associated with stopping said internal combustion engine is satisfied, said limit value being one of values of maximally retarded and advanced angles, respectively; second control means for controlling said mechanism to change said phase from said limit value if said predetermined condition is satisfied; first detection means for detecting an amount by which said mechanism is operated when said mechanism is controlled by said second control means; and second detection means for detecting said phase based on said amount, wherein said second control means includes means for controlling said mechanism to change said phase detected by said second detection means to attain a predetermined value.
 17. The control device for an internal combustion engine according to claim 16, wherein: said first control means includes means for controlling said mechanism to change said phase to said limit value after said internal combustion engine is stopped if said predetermined condition is satisfied; and said second control means includes means for controlling said mechanism to change said phase from said limit value after said internal combustion engine is stopped if said predetermined condition is satisfied.
 18. The control device for an internal combustion engine according to claim 16, wherein: said mechanism includes a motor electrically operated and having an output shaft rotating to change said phase in which said valve opens/closes; said first detection means includes means for detecting a number of rotations of said output shaft of said motor accumulated; and said second detection means includes means for detecting said phase as based on said number of rotations of said output shaft of said motor accumulated. 